1. Field of Invention
The present invention relates to the field of Uninhabited Air Vehicles (UAVs) and more specifically to a system and method for determining if the UAV is operating within its flight envelope.
2. Description of Related Art
The above-cited prior application disclosed a system and method for Automatic Flight Envelope Protection (AFEP) in a UAV. Generally, the system detected whether an operating command issued by the UAV would cause the UAV to exceed it flight envelope. If so, the AFEP routine would modify the operating command to the extent that operation beyond the flight envelope was preventable.
This system suffered from the drawback that the flight envelope was difficult to represent numerically so that operation beyond the flight envelope could be detected by computer and appropriate corrective action applied. For example, previous methods involved using an xe2x80x9cinterior blockedxe2x80x9d approximation, i.e., using cubes or rectangles to approximate the interior of the flight envelope. These methods were laborious to implement, and are in fact rather poor approximations of the flight envelope. A properly drawn V-N curve usually comes to a cusp at the low velocity limit, and is difficult to capture with a blocked approximation.
Interior blocked approximations also produced many artificial facets, which gives rise to numerous special conditions that must be tested, at the expense of addition computation, even though these limits are quite conservative because interior blocked approximations cannot fit the shape of the flight envelope very well. Thus the algorithm may indicate corrective action before it is actually necessary.
Further, it is normal for the aircraft to spend large portions of flights having the operating point quite close to one or more operating limits. Therefore, an inefficient representation of the flight envelope in the region of such limits will result in unduly constrained behavior of the aircraft.
In order to overcome these and other problems in the prior art, the present invention discloses a system and method for detecting if a UAV is operating within its flight envelope. The invention includes a means or step for defining the flight envelope of the UAV. The operating state of the UAV is identified from a present time to a future elapsed time. The invention determines if the UAV will be within its flight envelope at the end of the elapsed time in the future.